In the optical communication network, the WDM (Wavelength Division Multiplexing) technique has become widely used. Subsequent to the introduction of the WDM to the large capacity connection to the core network by Point-to-Point, the application of the WDM to the metro-local network and of the ROADM (Reconfigurable Optical Add/Drop Multiplexer) has been progressed. With the increase of the capacity of the wavelength path, more and more services will become multiplexed.
When the multiplexing degree is increased, a trouble occurred in the photonic physical layer has great influences on a plurality of upper service layers. Further, with the progress of the introduction of the ROADM, it is required to enhance the functions and the reliability of and decrease the cost for the node of the wavelength path network.
Patent Literature 1 (Japanese Patent Number 3533316) is a conventional technique of the enhancement of the reliability of the wavelength path network. FIG. 1 of Patent Literature 1 shows the basic configuration of a wavelength path multiplexing and demultiplexing optical transmission apparatus and an example of the switching when a trouble occurs. In this literature, FIG. 1(b) shows a trouble of the transmission path 52-1, and FIG. 1(b) shows a switching operation corresponding to the trouble of the optical transmitter 12-1.
In the trouble of the optical transmitter, the signal selector circuit 11 is switched such that the optical transmitter prepared for a redundant system is operated as the working system, and the sending wavelength of the optical transmitter 12-1 is switched to the wavelength of the wavelength multiplexing part 14 to send to the transmission path 52-1. Further, in the receiving side, the wavelength single outputted by the wavelength demultiplexing part 21 is received by the optical receiver 23-1 prepared as a redundant system. After switching the signal selector circuit 24 and cutting off the communication between switching operations, the communication before the occurrence of the trouble can be continued.
In the trouble of the transmission path 52-1, the sending wavelengths of the optical transmitters 12-1 to 12-m being the working system are respectively switched such that the output signal of the wavelength multiplexing part 14 is outputted to the transmission path 52-2 of a redundant system. The wavelength demultiplexing part 21, which has the same wavelength input and output characteristics with the wavelength multiplexing part 14, outputs the output wavelength signal to the optical receivers 22-1 to 22-m being the working system respectively, and after the communication is cut off between the switching operations, the communication before the occurrence of the trouble can be continued.
In the example of the configuration shown in FIG. 1 of Patent Literature 1, a case where two transmission paths which are the working system and the redundant system is shown. However, it is also possible to use a plurality of transmission paths. Further, the network can be extended by the optical bifurcation insertion node as shown in FIG. 9 of Patent Literature 1.
FIG. 1A shows a configuration of a wavelength path multiplexing and demultiplexing optical transmission apparatus according to a reference example for the present invention. In the configuration of the wavelength path multiplexing and demultiplexing optical transmission apparatus according to Patent Literature 1, a signal selector circuit is provided between the wavelength multiplexing/demultiplexing part and the optical transmitter/receiver as shown in FIGS. 3(b), 5(c), and 8(c). The sending side and the receiving side are connected by the wavelength signal via three or more transmission paths or a network (the routes 1506 to 1509).
The optical signals of the plurality of wavelengths λ1 to λ4 sent from the sending function part 1505 of the transponder is outputted to the wavelength multiplexing part output port #1 by the wavelength path multiplexing part 1502 via the optical matrix switch 1501, and sent to the receiving side via a transmission path or the network 1506. The optical signal inputted to the receiving side is received by the transponder receiving function part 1510 via the wavelength path demultiplexing part 1503 and the optical matrix switch 15804.
When a trouble occurs in the wavelength path multiplexing and demultiplexing transmission apparatus having the above configuration, it is required to simultaneously switch the transmission paths of the working system to those of the redundant system for coping with the trouble in a transmission path and perform a switching operation for coping with the trouble in the optical transmitter and the optical receiver. Furthermore, the operation of sending and receiving any wavelength signal for any transmission path or network is required.
Japanese Patent Application Publications JP-A-Heisei, 11-174253 and JP-P2006-197489A are other examples of conventional techniques relating to the optical wavelength multiplexing and demultiplexing system.